1. Field of the Invention
The present invention relates to a toroidal winding apparatus for forming winding wound around a trunk of a magnetic core having a central opening or window defined by the trunk.
2. Description of the Prior Art
As shown in FIG. 1 schematically, a conventional winding apparatus of this type has a circular magazine 2 which is rotatable around the center thereof passing through a central opening 1a of a magnetic core 1. The magazine 2 is supported rotatably by a frame (not shown) and is driven by drive means including a driving motor or a driving handle. The magazine 2 has an aperture 2a for pulling out the wire stored therearound which is defined by a pair of guide rollers 2b for guiding the wire 3 passing through the aperture.
In operation of the winding apparatus, after the core 1 is set against the blank magazine 2 as shown in FIG. 1, the magazine 2 is rotated, for instance clockwise, as shown by an arrow C in FIG. 1, to wind the wire 3 being fed from the drum means (not shown) by a predetermined length around the outer periphery thereof. The free end of the wire 3 having been wound up is pulled out inwardly through the aperture 2a and is fixed to the predetermined portion of the core 1. Thereafter, the magazine 2 is rotated anticlockwise, as shown by an arrow AC in FIG. 1, to form a coil having a predetermined number of turns around the trunk of the core.
In the winding appararus mentioned above, especially if the core is small size compared with that of the magazine, it is difficult to wind the wire tightly around the trunk of the core, since the wire is slacked off, as shown by dotted line in FIG. 1, during a travel of the aperture 2a from the position A remote from the core to the position B near to the core. This causes loose winding and, therefore, the coil is bulged to result in that the length of the wire required to form each coil becomes longer.
Also, it is to be noted that, in the winding apparatus mentioned above, the wire having been wound around the magazine is pulled out from the outer turn to the inner periphery of the magazine during forming process of the coils. Accordingly, the friction force applied to the wire being pulled out through the aperture becomes large due to the direct contact with the adjacent turns thereof and is varied due to the amount of the wire wound around the magazine. This causes uncertainty in the winding force and invites disadvantages as mentioned above.
These disadvantages in the conventional winding apparatus will be enhanced, when a thin strip of electrically conductive material is used to form a coil instead of a wire, as is disclosed in the JP-A-115805/1983.